Steve Webb’s idea of relaxing on holiday is to fill in complicated number puzzles.

But perhaps this geekiness is part of the reason why no politician has ever held this position for as long. He’s been in office since 2010. Before that the job switched hands ten times in a decade.

‘It was a revolving door,’ says Mr Webb. ‘I’ve had the great advantage of coming in at the start of the Parliament. Pensions is a long-term game, so you need time to see things through. In a way, this is the perfect job for me. You’ve got the social, human side of how pensions affect people’s lives, and then all that lovely technical detail.’

If you must: Steve Webb (right) said people should feel free to buy a Lamborghini with their pension savings.

While many politicians talk big and achieve little, you’d be hard pressed to level that accusation at Mr Webb.

In the past four years he has overseen the introduction of a new flat-rate state pension of £144 a week, promised a so-called triple-lock on how much it will be increased by every year (it will rise by the greater of inflation, wages or 2 per cent), and launched an automatic enrolment programme to get ten million workers a company pension for the first time.

Most recently and dramatically, he was the man behind the Budget’s revolutionary shake-up that will allow everyone the right to take their pension as cash, and avoid being ripped off by taking an income for life — an annuity.

He’s not finished yet. By the next election he wants to bring in a new type of pension — called defined ambition — that will ensure everyone gets out at least what they paid in.

The MP for Thornbury and Yate in Gloucestershire, he spends four days a week in Westminster, staying in a flat near the office.

Then it’s back-to-back meetings - he’d just met the head of the insurance industry trade body who’d been giving evidence to a committee of MPs. Afternoon is spent in Parliament, and then the evening at his office in the Commons answering queries from constituents.

Back at home he attends church every Sunday. Wife Helen is an ordained minister and they help out at a local breakfast club. She also volunteers for a pregnancy charity.

Before being elected as a Lib Dem MP in 1997, the 48-year-old studied Philosophy, Politics and Economics at Oxford University, then worked for the Institute of Fiscal Studies, specialising in research on taxes and benefits. He was appointed pensions spokesman in 2001.

But fate landed him the ministerial role. Conservative pension spokesman, MP Nigel Waterson, lost his seat in the General Election to a Lib Dem. Steve Webb was the logical, and only, choice.

STEVE WEBB: THE MINISTER WITH THE VERY SWEET TOOTH

Age: 48.

Marital status: Married to Helen, two children. Met in Clapham, London, where she was a curate.

Lives: Bristol.

Education: Dartmouth High School; Hertford College, Oxford.

Previous jobs: Institute of Fiscal Studies; Professor of Social Policy, University of Bath.

Hobbies: Maths puzzles, supporting West Bromwich Albion FC.

Working day: Spends four days a week in Westminster at a flat near the office of the Department for Work and Pensions. He gets to the office by 7.30am, reads the papers and trade titles over a cup of tea and piece of cake — he’ll vary which cake most days.

Meetings start from 8.30am, or he’ll work through ministerial boxes; the so-called ‘action folder’. In the afternoon he then heads over to Parliament and in the evening tries to tackle constituency issues at a separate office.

Downtime: Spends Saturday afternoon ‘walking round with my fingers in my ears so I can watch Match Of The Day without knowing how the Albion lost humiliatingly.’

He’s involved in his local church, going every Sunday, and helps Helen at a pregnancy crisis charity.

Today, he and Work & Pensions Secretary Iain Duncan Smith have become Westminster’s odd couple. IDS is renowned for his Right-wing stance on benefits and welfare, and Mr Webb is a liberal Lib Dem - but they’ve become close allies.

‘It’s actually Iain’s 60th birthday today,’ remembers Mr Webb. ‘I didn’t send him a card, which is remiss of me. It’s not a political statement, I forgot to send my goddaughter one recently, too.

‘I respect the fact that as an ex-leader of the Conservative party, he could have just gone off, not had any other grief or hassle and been a director of a dozen firms and had an easy life. But what does he do? He sets up a think-tank and devotes himself to social reform of the benefits system. You’ve got to respect that dedication. It helps that we’ve been working together for four years now.

Pensions: Deal Finders

‘We can look back and say: yes, that was a success. When it comes to pensions I think he trusts my judgment.’

Mr Webb brands the recent Budget reforms on annuities a real Coalition triumph. And it stemmed from his brainwave.

It was after the plans for the flat-rate state pension were finalised that he first started talking loudly about the need to get rid of restrictions on how much cash people could take from their nest eggs.

The logic was that with no more means-tested benefits for pensioners, it meant that if people spent their nest eggs all at once, there would be little extra they could claim from the state.

He began cautiously sounding out the Treasury about removing the caps on drawdown schemes (a type of pension that allows retirees to take their pension in chunks). But when an investigation by the City regulator the Financial Conduct Authority into the way annuities were sold found widespread problems, it made reform even more critical.

‘The things that had been stopping us before were the means-testing of benefits for state pensioners, and paternalism. All the rules we had were based on the old pension system. So the new single-tier pension makes all this possible.

‘I’m not the minister responsible for annuities. But because we had all these pots that we are going to create under auto-enrolment, I had very strong views on the subject. So I’ve been banging on and pressing for action. I’d suggested an annuities task force and we had agreed we were going to announce something in the Budget. The Chancellor was very enthusiastic and decided to go further.’

George Osborne’s announcement shook the insurance industry. Since then, the debate has been over whether retirees can be trusted not to blow their pensions on a Lamborghini.

The day after the Budget Mr Webb hit the headlines when he said he did not have a problem if retirees spent their entire pension on this fast car.

‘Because of that comment I managed to get on page two of the Sun without a scandal. For a government minister I take that as some sort of achievement,’ he jokes.

‘It’s worked out fine because although most people can’t buy a sports car, why should I tell people what they can spend their money on? That’s an important issue that’s been highlighted.’

Yet it must be frustrating for a man with an economics degree to have to admit that there is no research to prove they won’t.

‘What you can look at is how people spend the tax-free lump sums they take from their pension. Many people don’t spend all that, and a quarter don’t even take the lump sum,’ he adds.

He is working on plans to ensure that everyone who retires gets guidance. Part of this could include showing pensioners figures showing when they might die.

He adds: ‘People have a very poor estimate of how long they might live for. But that is fundamental to understanding how you might spend your pension.’

For the most part, Steve Webb’s Westminster office is functional, and a little tatty — with furniture that wouldn’t be out of place in a sixth-form common room.

Three oil paintings with thick gold frames hang on one wall, oddly out of place. Between them is another modern artwork that looks as if someone has just scrawled on a whiteboard in blue marker pen.

A clunky old PC has been shoved to one side of his desk, and in the middle a laptop is open.

A West Ham United football shirt hangs off a book case. It’s not because he supports the Hammers (he’s a West Bromwich Albion fan), but rather because of another achievement that happened at the London club. The words on the back give a clue: three million.

‘The three-millionth person to be automatically enrolled in to a pension was a groundsman at West Ham. That’s a remarkable achievement. That’s three million people now in a pension that 18 months ago didn’t get one.’

This pride is typical of the way he talks about his reforms, but he is at his most animated when questioned about how the state pension changes affect women.

In opposition, he had been a fierce campaigner for women’s pension rights, fighting to ensure mums were not penalised for taking time off work to raise a family.

Now though, around 700,000 women born between April 6, 1951 and April 5, 1953 feel as if their champion has betrayed them.

They are being forced to work longer because their retirement age has increased, but they will still miss out on the new flat-rate state pension.

Mr Webb leaps from his armchair, grabs a sheet of paper and a pen and begins scrawling a chart.

It shows how women who retired before 2010 had to pay in 39 years of National Insurance contributions to claim a full state pension, but could claim their state pension age at 60.

Those retiring between 2010 and 2016 need just 30 years of contributions, but will claim once they are between 60 and 63. Then, post 2016, 35 years of contributions are needed, and retirees will be aged 63 and upwards — but these will claim the new flat-rate state pension.

From 2010, those claiming state pension have also benefited from the triple-lock, which promises it will increase each year by the higher of either wages growth, inflation or 2 per cent.

‘You tell me which of these groups you think is better off?’ says Mr Webb. ‘You’d be hard pressed to tell me which one it is.

More choice: People retiring from next April will be able to dip into their pension whenever they want.

‘Do I understand why they feel angry? Absolutely I do, partly because they think that if they retired in April 2016 they would get £144, when actually they wouldn’t on average.’

This is because they would not have contributed enough National Insurance.

Mr Webb says he is sympathetic because they didn’t know their state pension age was changing, as this was a change made two decades ago — though not made widely public at the time.

There are more things he would clearly like to get his teeth into. The Lib Dems want to reform tax relief on pensions.

Currently putting £1 in a pension costs a basic rate taxpayer 80p, but 60p for a higher rate taxpayer and just 55p for a top rate payer. He’d rather have a flat benefit for all — and likes the idea that £1 should cost everyone just 70p.

And he has his eyes on the lifetime allowance on pensions. Currently anyone with more than £1.25 million in a scheme gets hit with a 55 per cent tax charge.

He says: ‘The lifetime allowance is a funny thing because it doesn’t just say if you pay in more than this you don’t get tax relief, we actually have a penal rate of tax. To actually say that we will punish you if you go beyond our limits seems illiberal to me.’

His two children are teenagers. So what kind of pension does he think they’ll end up with?

‘It won’t be a final salary scheme, but I’ve made it much more likely that there will be a state pension when they retire. It won’t be a king’s ransom though.

‘And there won’t be such a thing as retirement day as such. They’ll be in second jobs, third jobs, part-time work.

‘It’ll be much more a process as each generation is working longer. It’ll just be a different culture. The days of the gold watch retirement day are probably over.’